Blood clotting, a process that relies on adhesion of platelets and proteins to a surface as a first step, can be a problem when blood is introduced into a microfluidic device. Undesired clot formation can make many desired blood tests impossible. Heparin coating of surfaces can control blood clotting to a limited extent. See Barstad, R. M, et al., Thrombosis and Haemostasis 79, 302-305 (1998). Certain polymeric species, such as polyethylene glycol (PEG) chains, can influence the surface hydration layer to prevent protein adsorption. See Chen, S. et al., Polymer 51, 5283-5293 (2010). However, they are not fully effective and soluble anticoagulants still must be added to the blood.
What is needed is better control over blood clotting in a microfluidic device.